Apparatus for electroplating a ribbon



NOV. 3, 1970 GREEN 3,537,971

APPARATUS FOR ELECTROPLATING A RIBBON Filed Aug. 7, 1967 United States Patent 3,537,971 APPARATUS FOR ELECTROPLATING A RIBBON Ralph J. Green, Newark, N.J., assignor to RCA Corporation, a corporation of Delaware Filed Aug. 7, 1967, Ser. No. 658,852 Int. Cl. B01k 3/04; C23b 5/68, 5/58 US. Cl. 204211 9 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION When a substrate of ribbon form is run through an electroplating bath for the purpose of depositing thereon a layer of plating material, due to the fact that the ribbon is completely surrounded by the electrolyte, the density of current flow to the ribbon is greater in the volume of the bath adjacent to the narrow edge of the ribbon than adjacent to the flat sides of the ribbon. Therefore, more material is plated on the edges, and in the vicinity of the edges, of the ribbon, than on the flat sides of the ribbon, whereby after the plating is completed the ribbon has a cross sectional shape resembling that of a dumbell. This cross sectional dumbell shape of the plated ribbon may have many disadvantages. The excess of plating material over a uniform thickness is wasted material. The excess material may prevent operation of the ribbon as desired, and this excess material decreases the packing density of the ribbon when it is wound in a coil form.

It is an object of this invention to provide means for uniformly plating a thin ribbon with plating material.

SUMMARY OF THE INVENTION In accordance with the invention, a sheath shaped as a flat tube and constructed of material such as Mylar which is not affected by the electrolytic bath in which it is to be immersed, is provided. The ribbon to be plated is run through the sheath in a continuous manner. Holes are provided along the length of the sheath, the holes being of any desired shape, whereby the edges of the ribbon in the sheath are less exposed to the electrolyte than the middle portion of the ribbon. The holes are so shaped and positioned that the thickness of the layer electroplated on the ribbon through the holes, as the ribbon is drawn through the sheath, is uniform.

BRIEF DESCRIPTION OF THE DRAWING The invention will be better understood upon reading the following description in connection with the accompanying drawing, in which FIG. 1 is a plan view of an electrolytic plating apparatus according to the present invention, and

FIG. 2 is an enlarged view of the line 2 2 of FIG. 1 of a section of the ribbon to be plated and of the sheath through which it is drawn.

DESCRIPTION As shown in FIG. 1, a tank 10 is provided having electrolyte 12 therein. A pair of electrodes 14 of a material to be plated on a ribbon 16 are immersed in spaced relation in the electrolyte 12, and the positive terminal 18 of a source of plating current (not shown) is connected to each of the electrodes 14. A sheath 17 of a material "ice which is not harmed by the electrolyte 12 hangs down between two crossbars 20 and 22 which are fixed to the tops of opposite walls of the tank 10. The sheath 17 which is positioned substantially half way between the electrodes 14, may comprise one sheet of a material such as Mylar folded over on itself. The folded edge may be clamped and heat treated, but not fused while clamped, to relieve strain in the material and to produce a sharp stress-free bend 19 that will not open when the sheath 17 is immersed in the plating electrolyte 12 even when the electrolyte 12 becomes hot. The contacting portions of the folded over sheet are then fused together as at 21. The sheath 17 has holes 24 therethrough permitting the ribbon 16, which extends through the sheath 17, to be exposed to the electrolyte 12. Sliding contacts 26 are provided for the ribbon 16, the contacts 26 being positioned outside the tank 10 and at opposite sides thereof. The contacts 26 are connected to the negative terminal 28 of the DC. source (not shown). The sheath 17 hangs down into the electrolyte 12 and the ends of the sheath 17 are fixed to the tops of opposite walls of the tank 12 as by the crossbars 20 and 22. The ribbon 16 may run from a roll 30 thereof through the sheath 17 and after running through a water rinser (not shown) may be rolled on a roll 33. The ribbon 16 may be caused to travel through the sheath in any known manner as by a belt-driven pulley 34 mounted for rotation with the shaft 36 on which the roll 33 is wound.

A section of the ribbon 16 and the sheath 17 showing the holes 24 therein to expose the ribbon 16 to the electrolyte 12 as shown in FIG. 2.

If the ribbon 16 were run through the 'bath 12 without using the sheath 17, more plating material would be deposited on the narrow edges ofthe gribbon 16 than on the flat sides 32 thereof, whereby-pas noted above, the cross sectional shape of the ribbon16, after plating, would assume a dumbbell shape. The holes 24 are so shaped and arranged that more of the flat sides 32 of the ribbon 16 is exposed to the electrolyte 12 than the edges 31 of the ribbon 16. Therefore, the plating of the sides 32 of the ribbon 16 is relatively increased in thickness with respect to the plating on and near the edges 31, thereby to equalize the thickness of the plated layer on the ribbon 16 whereby the plating on the ribbon 16 may be made substantially uniform. The round shape of the holes 24 and their central location is shown in FIGS. 1 and 2 by way of example only. The holes may take any shape and any arrangement to accomplish the end of causing substantially uniform plating. It should be noted that to accomplish uniform plating, the ribbon must be drawn through the sheath, which is immersed in the solution, in a relatively uniform manner, since at any instant the thickness of the plating will be greatest in registry with the holes 24. Due to the motion of ribbon thru the tank the edges of the ribbon and the sides of the ribbon in the vicinity of the edges are in effect plated for a less period of time than the other side portions of the ribbon. Motion of the ribbon with respect to the sheath results in an averaging effect and therefore in a uniform plating on the ribbon 16.

While the described plating device is of general application, it is useful to plate silver uniformly on a ribbon comprising a substrate which may be of stainless steel, on which niobium tin superconductive material has been plated as by vapor deposition.

Modifications of the described plating apparatus will be apparent to persons skilled in the art. For example, while the sheath is shown as being constructed of one piece of sheet material folded over, it can be made of two sheets whose lateral edges are fixed together. The sheath 17 may extend between submerged weirs (not shown) in opposite end walls of the tank and the level of the electrolyte 12 may be maintained by pumping. Therefore, the above description is to be taken as illustrative and not in a limiting sense.

What is claimed is: 1. An electrolytic plating apparatus in which a fiat ribbon having two flat sides and two edges is to be plated with a uniform thickness of plating material comprising:

a container for an electrolytic solution; means for passing said ribbon through said solution in a given direction and for applying a potential of one polarity to said ribbon;

at least one electrode immersed in said solution and having a potential of opposite polarity applied thereto, whereby the density of the current flow from said electrode to said ribbon through said solution is greatest adjacent to said edges of said ribbon on at least one of said flat sides of said ribbon; and a sheath through which said ribbon is passed while being passed through said solution, said sheath having therein a single column of holes parallel to said given direction, the total of the dimensions of said holes along any one of a plurality of given paths parallel to said given direction being inversely proportional to the density of the current fiow at said one given path. 2. The invention according to claim 1 wherein there are two electrodes immersed in said solution and said sheath is positioned between said electrodes.

3. The invention according to claim 1 wherein said sheath is a fiat tubular shaped element having two fiat sides and of a material which is not harmed by said solution, said holes bein'g through each of said fiat sides.

4. In combination: a tank containing an electrolytic solution and at least one electrode immersed in said solution, there being a potential of one polarity applied to said electrode;

a sheath having two ends fixed to said tank and positioned in said tank such that at least a portion of said sheath is entirely submerged in said solution; and

means for moving through said sheath in a given direction a ribbon of opposite potential polarity which is to be uniformly plated;

said sheath being of flat tubular shape thereby having two flat sides and two narrow edges, at least one of said flat sides having therein a single column of holes parallel to said given direction, the total of the dimensions of said holes along any one of a plurality of given paths parallel to said given direction decreasing as the location of said one given path is removed from a path parallel to said direction and located at the center of said sheath.

5. The invention according to claim 4:

wherein there are at least two electrodes immersed in said solution, each having said potential of one polarity applied thereto, and

wherein said sheath is of a material which is not harmed by said solution and each of said two narrow edges of said sheath are respectively closer to one of said two electrodes than are said two fiat sides.

6. The invention according to claim 4 wherein each of said holes has the same dimensions.

7. The invention according to claim 4 wherein said sheath is of a material which is not harmed by said solution and each of said flat sides have said single column of holes therein.

8. The invention according to claim 7.

wherein there are two electrodes immersed in said solution each having said potential of one polarity applied thereto, and

wherein each of said two narrow edges of said sheath are respectively closer to one of said two electrodes than are said two flat sides.

'9. The invention according to claim 7 wherein each of said holes has the same dimensions.

References Cited UNITED STATES PATENTS 2,445 ,3 72 7/ 1948 Trenbath 204-28 2,868,702 1/ 1959 Brennan 204-28 2,930,739 3/1960 Burnham 204-28 3,316,160 4/1967 Uchida et a]. 204-28 3,324,022 6/ 1967 Keeleric 204-206 XR FOREIGN PATENTS 255,736 7/ 1926 Great Britain.

JOHN H. MACK, Primary Examiner W. B. VAN SISE, Assistant Examiner US. Cl. X.R. 204-206, 28 

